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WHAT'S UP: Nobel Prize awarded for discovery of universe expansion

Oct 14, 2011

The three recipients of the 2011 award are Saul Perlmutter from the Lawrence Berkeley National Laboratory and the University of California, Brian P. Schmidt from Australian National University, and Adam G. Riess from Johns Hopkins University and Space Telescope Science Institute in Baltimore.

To these scientists, the Nobel Prize in Physics means fame and fortune. They will share the monetary prize of 10 million Swedish krona —5 million for Perlmutter, and 2.5 million each for Schmidt and Riess.

At the present exchange rate, 10 million Swedish krona is about $1.5 million.

But what does this mean to you and me?

It has been known for nearly a century that the universe is expanding. In every direction we look, distant galaxies are observed to be moving away from us (and each other) at a speed that is roughly proportional to distance. The farther a galaxy, the faster it is receding.

This is perhaps the most compelling evidence for the “big bang” theory of the universe. If now, galaxies are far apart and moving still farther apart, at some time in the past everything must have been closer together.

By measuring the so-called Hubble Constant — a number that tells how fast a galaxy at a given distance is receding — we can measure both the maximum size and age of the universe. Present best-estimates put the age of the universe at 13.8 billion years.

So far, so good; but here the going will get a little strange.

One naively might expect that the expansion of the universe will decrease as time goes by. If the “big bang” was like an explosion that cast the galaxies apart against their mutual gravitational attraction, slowly, over time, one might expect gravity to win.

One might expect gravity to slow the expansion, and perhaps eventually draw all the matter back into itself — resulting ultimately in a fiery big crunch, a reverse “big bang.”

There are ways to test this expectation observationally. One is to look for very distant, very bright objects that have the same intrinsic brightness, and work out from these observations how far away each object is and how fast it is moving.

Remember, the farther away in the universe we look, the farther back in time we see, because light travels at a fast but finite speed. A picture of a galaxy 6 billion light-years away shows us how that galaxy looked 6 billion years ago.

Perlmutter, Schmidt and Riess looked for and found hundreds of distant type Ia supernovae — exploding sun-like stars (like the one that recently flared up in the Pinwheel Galaxy just 21 million light-years away).

From their observations, they worked out that instead of slowing down, or even remaining constant, the expansion of the universe is increasing with time. In the past, the universe expanded more slowly than it is now. In the future, it will be expanding more rapidly.

Something is pushing all matter in the universe apart; something stronger than gravity. What is it? Scientists are not sure.

Some say dark energy — an unknown form of energy that accounts for almost three-quarters of all the energy in the universe — is accelerating the expansion of the universe. Others have different ideas.

Maybe it is the hand of God.

— By Doug Furton, a member of the physics faculty at GVSU. Send questions and suggestions to dgf@inbox.com.